Embryonal Hyperplasia of Bowman’s

H&E and PAS-stained sections from the kidney of an 8-year-old male with advanced nephrosclerosis of unknown etiology. An exuberant proliferation of epithelial cells with an embryonal or immature appearance, arranged in a tubular and nodular pattern, is seen surrounding globally sclerotic glomeruli. This unusual finding termed “embryonal hyperplasia/metaplasia of Bowman’s capsule epithelium” has been described in patients with end-stage renal disease on long-term dialysis. More recently, this finding has also been associated with WT1 mutations in patients with Denys-Drash syndrome and isolated diffuse mesangial sclerosis. The clinical significance of this finding is yet to be determined.